Abstract

A chert bed in the Whitehall Formation (Cambrian and Ordovician) of eastern New York State is strikingly similar in petrography and inferred origin to Australian and South African silcretes. The chert in the Whitehall, like its Australian and South African counterparts, occurs along an erosion surface that formed subarially, and it contains colloform chalcedony and abundant ferruginous minerals. This chert also contains pseudomorphs and ghosts of halite. Silica precipitated from a solution that became enriched in electrolytes as a result of dissolving halite. Sand-size chert grains in the Whitehall are petrographically like the Whitehall silcrete and are probably grains of reworked silcrete.